bact growth: physical and chemical requirements Flashcards
what is bacterial growth?
increase in the NUMBER of cells and not the size of cells
how do bacteria multiply?
binary fission (asexual)
what is generation time?
time required for one cell to become two cells
what are the two measurements of bacterial growth?
direct method
indirect method
what is the direct method of measuring bacterial growth?
- microscopic counts
- viable counts
what is microscopic counts?
both live and dead cells are counted (total cell count)
what are viable counts?
only live cells are counted
what is serial dilution?
in viable counts: samples are diluted, generally 10-fold, to be counted
what are indirect methods of measuring bacterial growth?
- measure turbidity in a spectrophotometer
- absorbance or optical density
what are the four phases of bacterial growth on the growth curve?
lag, log, stationary, death
what are the physical requirements of bacterial growth?
oxygen, CO2, temperature, pH, and osmotic pressure
what are the chemical requirements of bacterial growth?
nutrients
what are the 3 types of aerobes?
-obligate
-facultative
microaerophilic
what is the relationship to O2 and type of energy metabolism of obligate aerobes?
- required
- aerobic respiration
what is the relationship to O2 and type of energy metabolism of facultative aerobes
- O2 not required by better growth with O2
- aerobic respiration and fermentation
what is the relationship to O2 and type of energy metabolism of microaerophillic aerobes?
- O2 required but at a lower concentration
- aerobic respiration
what is the relationship to O2 and type of energy metabolism of aerotolerant anaerobes?
- O2 not required
- fermentation
what is the relationship to O2 and type of energy metabolism of obligate anaerobes?
- O2 not required, its harmful
- fermentation
what are the toxic forms of oxygen
- singlet oxygen
- superoxide oxygen
- peroxide anion
- hydroxy radical
how do toxic forms of oxygen inhibit or kill bacteria?
by disrupting nucleic acid and protein structures
what 3 enzymes detox oxygen radicals?
- catalase
- peroxidase
- superoxide dismutase
what is required for biosynthesis?
carbon dioxide
what bacteria thrives in temps 10 to 15 C?
psychrophiles
what bacteria thrives in temps 30 to 37 C
mesophiles
what bacteria thrives in temps >55 C
thermophiles
what is the optimal physiological pH?
6.8-7.2
are fungi bothered by pH?
no, they are acid tolerant
what is the physiological ionic strength?
0.65% NaCl
2 requirements for chemical growth
carbon and energy
carbon required for chemical growth
CO2 and organic
energy requirements for chemical growth
light or chemical
pathogens have what chemical requirements for growth?
organic molecules for energy and carbon
nutrient requirements: macronutrients
carbon, nitrogen (others like S, K, P, Na, Ca etc)
nutrient requirements: micronutrients
Metals (Cu, Ze, Fe, Mn, Mo, etc)
what metal plays a major role in respiration?
iron
host Fe is tied up to what proteins?
transferrin and lactoferrin
what are siderophores?
- iron-binding agents produced by bacteria
- enterobactins (E. coli and Salmonella)
- bind to Fe and transport to cell
what is culture medium?
nutrient solution required for growth
- liquid (broth)
- solid (agar)
what is inoculum?
bacterial cells to the medium to initiate growth
what is culture?
bacterial growth in a medium
what is a defined medium?
exact chemical composition is known, pure chemicals are used
what is a complex medium?
chemical composition is not know. has complex substances
what is a general purpose medium?
allows growth of most bacteria
what is a selective medium?
suppresses growth of unwanted bacteria and promotes growth of desired bacteria
what is enrichment medium?
a liquid medium designed to increase growth of a desired bacteria
what is differential medium?
differentiates two or more types of bacteria. -generally a solid medium
